Signal generating arrangement for an electric typewriter and similar apparatus



NOV. 14, v p MASON ET AL SIGNAL GENERATING ARRANGEMENT FOR AN ELECTRIC TYPEWRITER AND SIMILAR APPARATUS .Filed Sept. 20. 1965 Inventors v FREDEQICK MASOA/ GRAHAM J. L. STEVENS United States Patent M 3,353,038 SIGNAL GENERATING ARRANGEMENT FOR AN ELECTRIC TYPEWRITER AND SIMILAR APPARATUS Frederick P. Mason and Graham J. L. Stevens, Hollingbury, Brighton, England, assignors to Creed & Company Limited, Brighton, England, a British company Filed Sept. 20, 1965, Ser. No. 488,317 Claims priority, application Great Britain, Nov. 6, 1964, 45,303/64 2 Claims. (Cl. 310-82) The invention relates to a key-operated signal generating arrangement for an electric typewriter, teleprinter or other key-operated apparatus wherein depression of a key is required to cause an electric signal to be transmitted elsewhere or to set in train various electrical and/or mechanical interconnections.

In certain classes of such apparatus the keys of a keyboard are required to do no more than generate an appropriate signal without mechanical linkage to other members, such as typebars, interlocking arrangements and so forth. What is then desirable is that depression of a key shall set up an electrical control signal which persists for as long as the apparatus is under the control of that particular key. When it is desired that the actuation of a key should generate its own conrtol signal it is possible to use for this purpose a piezo-resistive or a piezoelectric element particular to the key. The advantage of using a piezo-resistive element is that such an element exhibits a resistance change which continues for so long as the mechanical force applied to it remains, in other words, for so long as the key remains depressed. It may be mentioned, in this connection, that it is possible to arrange that a key, once actuated, remains locked down until its function has been performed. On the other hand, the nature of a piezo-electric element is such that it generates a finite electrical charge for a finite mechanical strain to which it is subject, and in practice the value of this charge is such that the element would not be capable of delivering to a circuit having a practical value of resistance a signal persisting for the time required in normal keyboard operation. Against this, however, is to be set the fact that a pieZo-electric element is much cheaper than the equivalent piezo-resistive element.

In the present invention the above mentioned difficulty in using a piezo-electric element for keyboard operation is overcome by arranging that actuation of a key subjects the element to vibratory strain.

According to one aspect of the present invention there is provided a signal generating arrangement for an electric typewriter, teleprinter or other key-operated apparatus including a pieZo-electric crystal element and a key mechanically coupled together in such manner that actuation of the keybar causes the piezo-electric element to be subject to alternating strain and the relay generate an electric signal of substantial duration.

According to another aspect of the invention there is provided a keybar arrangement for an electric typewriter, teleprinter or other ke -operated apparatus, including a keybar, a vibratory cantilever, a piezo-electric crystal element mounted on the cantilever and arranged to generate an electric signal upon vibratory flexure of the cantilever, magnet means causing the cantilever to be mechanically coupled to the keybar so as to follow its movement over a given range, and means causing disengagement of the cantilever from the keybar and consequent vibration of 3,353,033 Patented Nov. 14, 1967 ICC the cantilever when the movement of the keybar exceeds the given range.

An embodiment of the invention will be described with reference to the accompanying drawing which shows, diagrammatically, a side view of a keybar and the components associated therewith for setting a piezo electric element into vibration and thus generating an electric signal of substantial duration.

The embodiment illustrated has a keybar 1 mounted for pivotal movement about a pin 10 in the directions indicated by the arrows A and B. The keybar is shown in its rest position, to which it is urged by a return spring 2 against an upper limit stop 11, the spring working against and the stop being mounted on a mounting frame, portions only of which are indicated at 3. The free end of the keybar carries a conventional typewriter key 12.

A vibratory cantilever 4, of elastic material such as spring steel, is clamped at one end at 5 above the keybar. Mounted on the cantilever so as to be subject to vibratory flexure with the cantilever is a piezo-electric crystal element 6 connected to a pair of output leads marked OP.

A permanent magnet 9 is secured to the keybar 1 and, in the rest position of the keybar, attracts against it the cantirever 4, or, in the case where the cantilever is of nonmagnetic material, an armature 8 secured to the cantilever 4.

A stop member 7 is mounted on the frame 3 below the free end of cantilever 4.

When, now, the key 12 is depressed, the keybar 1 carries with it magnet 9, which draws downs the cantilever until it engages the stop member 7. Further downward movement of keybar 1 forces the magnet to disengage from the cantilever or its armature, as the case may be; the cantilever is now free to vibrate and cause flexural vibration of the piezo-electric element and consequent generation of an alternating electric signal voltage across the output leads OP. The key may be considered to be actuated when it has been depressed to the extent necessary to free the cantilever. In the normal arrangement, as discussed above, it will then be locked, by means not shown until the associated apparatus is ready to perform a new key-controlled function. On being returned to its rest position, the magnet 9 re-engages the cantilever on its armature and the cantilever is once more mechanically coupled to the keybar.

It is to be understood that the following description of specific examples of this invention is made by way of example only and is not to be considered as a limitation on its scope.

What we claim is:

1. A keybar arrangement for key-operated apparatus comprising a keybar, a vibratory cantilever, a piezo-electic crystal element mounted on the cantilever and arranged to generate an electric signal upon vibratory flexure of the cantilever, magnet means causing the cantilever to be mechanically coupled to the keybar so as to follow its movement over a given range, and means causing disengagement of the cantilever from the keybar and consequent vibration of the cantilever when the movement of the keybar exceeds the given range.

2. A keybar arrangement as claimed in claim 1 wherein the keybar is a lever pivoted at one end for rotation in a vertical plane when the arrangement is placed in its normal attitude for use, return spring means being provided for returning the keybar after depression to a rest position, wherein the magnet means includes a magnet attached to the keybar, the cantilever arranged to be attracted against the magnet when the keybar is in its rest position, the cantilever being mounted above the keybar, and wherein a stop member engages the cantilever and effects disengagement between the magnet and canti lever when the keybar is depressed beyond the position corresponding to engagement of the cantilever with the stop member.

References Cited UNITED STATES PATENTS 2,302,081 11/ 1942 Weitmann 310-85 5 2,309,703 2/ 1943 Lovell 310-82 2,464,045 3/ 1949 Kuenstler 310-80 2,921,252 1/ 1960 Schiavone 310-85 MILTON O. HIRSHFIELD, Primary Examiner.

10 J. D. MILLER, Assistant Examiner. 

1. A KEYBAR ARRANGEMENT FOR KEY-OPERATED APPARATUS COMPRISING A KEYBAR, A VIBRATORY CANTILEVER, A PIEZO-ELECTIC CRYSTAL ELEMENT MOUNTED ON THE CANTILEVER AND ARRANGED TO GENERATE AN ELECTRIC SIGNAL UPON VIBRATORY FLEXURE OF THE CANTILEVER, MAGNET MEANS CAUSING THE CANTILEVER TO BE MECHANICALLY COUPLED TO THE KEYBAR SO AS TO FOLLOW ITS MOVEMENT OVER A GIVEN RANGE, AND MEANS CAUSING DISENGAGEMENT OF THE CANTILEVER FROM THE KEYBAR AND CONSEQUENT VIBRATION OF THE CANTILEVER WHEN THE MOVEMENT OF THE KEYBAR EXCEEDS THE GIVEN RANGE. 